Components derived from microorganisms have immunoreactivity. In particular, it has been known that DNA contained in a large amount in the bacterial components of Mycobacterium tuberculosis has strong action to activate natural immunity and functions as an adjuvant for inducing a T helper type 1 immune reaction to an antigen (Science 273; 352-354, 1996). It has also been known that the action of this DNA to activate immunity is derived from DNA having a CpG motif (CpG DNA) and that such immunoreactivity is lost by alternation of the sequence or methylation of cytosine (Nature 374; 546-549, 1995).
On the other hand, there has been a report suggesting the possibility that such DNA derived from microorganisms is associated with the pathologic conditions of autoimmune diseases including articular rheumatism as a typical example (Arthritis Rheum 43; 2578-2582, 2000, Nature 416; 603-607, 2002).
JP Patent Publication (Kohyo) No. 2002-521489 A describes that the S-stereoisomer of DNA containing CpG is able to stimulate immunity, and that such CpG-containing DNA can be used as a vaccine adjuvant, or as a factor for activating immunity to prevent or treat virus diseases, parasitic diseases, or fungus diseases, or it can also be used in immunotherapy for cancers, allergic diseases or asthma. Moreover, JP Patent Publication (Kohyo) No. 2002-521489 A also describes that the R-stereoisomer of CpG-containing DNA is able to suppress the aforementioned effect of the S-stereoisomer to stimulate immunity.